Anchorage,
Alaska is a modern city with more than 250,000 people. Scientists
are studying ways to improve salmon runs into streams that flow
through the city.

Saving City Salmon
__________________

INTRO: As Alaska's cities get bigger, streams that
once supported healthy runs of salmon now find themselves polluted,
re-routed or otherwise altered. Chester Creek is one such stream. It
flows through the center of Anchorage, Alaska's largest city. As Doug
Schneider reports in this week's Arctic Science Journeys Radio, a scientist
who studied the creek offers suggestions to save the creek's city salmon.

STORY: Photographs taken in the early 1900s show
early day settlers harvesting salmon along Chester Creek, when it was
still just a place in the vast Alaska wilderness. Today, Chester Creek
is an urban salmon stream, set mid the hustle and bustle of Anchorage's
250,000 people. The creek begins high in the still undeveloped Chugach
Mountains north of the city, but then quickly finds itself winding through
the many neighborhoods, busy streets, and business parks of the city's
midtown section.

Ultimately, the stream empties into Westchester Lagoon, an artificial
lake created by a small dam and culvert system near the mouth of the
creek. Culverts allow the water to flow from the lagoon into the nearby
ocean.

A lot has changed since the first settlers came to Alaska. What was
once a vibrant salmon stream now hosts only a small run of wild coho
salmon. In a state famous for salmon, urbanization is taking a toll
on the state's inner-city salmon streams. Matthew Whitman is a graduate
student at the University of Alaska Fairbanks who studied the impacts
of urbanization on Chester Creek and its salmon.

WHITMAN: "Well, it's in the northern region of Anchorage. If you're
familiar with Anchorage, it's one of the older and more developed parts
of the city. Historically there was a large coho salmon run in that
stream. Since the 1950s there has been major development in that part
of the city and today there is only a remnant population of salmon that
return to the stream."

Chester
creek was once a wilderness stream, but as Anchorage grew, the creek's
salmon runs declined. Chester creek today can still be seen where
it flows through a greenbelt in the city's midtown section. Click
on the image above for a larger view.

To learn why salmon aren't doing well in Chester Creek, Whitman first
had to understand the characteristics of a healthy salmon stream. He
reviewed hundreds of studies on salmon streams across the country and
came up with a kind of checklist.

To start, good salmon streams should offer a diversity of habitats-places
with woody debris for small fish to hide, for example. Steams should
have stretches of riffles, along with stretches of pools; some deep,
and some shallow. Salmon also need unfettered access to good spawning
areas. Log jams, bridges, dams, and other impediments are the kiss of
death to salmon. The water temperature needs to be just right, and there
needs to be plenty of dissolved oxygen and nutrients like phosphorous
and nitrogen.

WHITMAN: "What else do they need? Well, there are other important
things to look at in the streambed itself. Are there gravels and cobbles
and are they suitable size for spawning? Are there too many fines of
a certain size that would choke of the nests so that there isn't good
water flow into the reds during the incubation phase?"

According to Whitman, Chester Creek falls short in several of these
key requirements. Habitat diversity is lacking. Where once trees and
brush shaded the waterway, paved roads now cross its path, while parking
lots and manicured lawns stretch to its banks in many places. The creek
also is too shallow in spots, and at times the water is too hot and
has too little oxygen. Whitman says culverts bring runoff along with
pollutants and sediment into the creek. The runoff can be intense at
times, and can wash away salmon eggs and destroy habitat. But most troublesome
are the human barriers—bridges, culverts, and dams—that
impede salmon migration. Whitman says the most important barrier is
the dam and culvert system at the mouth of the creek itself.

Bridges,
culverts and dams create barriers to adult salmon returning to
spawn. Runoff that carries pollution, sediment and high water
also pose a threat to the survival of the creek's wild salmon.

WHITMAN: "There is a problematic barrier at the mouth of the creek.
Adults can make it through but it's widespread knowledge that it is
very inefficient and difficult."

To be sure, Chester Creek isn't the only salmon stream running through
Anchorage. Nearby, Campbell Creek and Ship Creek continue to support
salmon, and studies of their health also are underway. And just outside
town, in an area that is under increasing development pressure, is Rabbit
Creek. Presently the stream hosts a healthy run of wild salmon. But
Whitman says that could change.

WHITMAN: "Rabbit Creek is in an area that is being developed, so it
might be important to learn some things from Chester Creek and apply
them to Rabbit Creek so we don't see the same sort of things happen
to coho salmon in that stream."

Whitman says community groups are organizing efforts to rehabilitate
Chester Creek. He hopes his study will help them decide what problems
to tackle first. Anchorage isn't the only large Alaska city with urban
salmon streams, either. The Chena River, which runs through the center
of Fairbanks, also has come under increased development pressure and
declining salmon returns.

This is Arctic
Science Journeys Radio, a production of Alaska Sea
Grant. I'm Doug Schneider.

Audio version (sidebar at top right)
Thanks to the following individuals for help preparing this script:

Arctic Science Journeys is a radio service highlighting science, culture,
and the environment of the circumpolar north. Produced by the Alaska Sea
Grant College Program and the University of Alaska Fairbanks.